Irradiance-controlled fixture for horticultural applications

ABSTRACT

Various implementations disclosed herein includes a method for operating lighting fixtures in horticultural applications. The method may include receiving a user input of a desired irradiance for a first color channel of one or more lighting fixtures that irradiates a plant bed, in which each of the one or more lighting fixtures comprises at least one light emitting diode (LED) array, determining, for each of the one or more lighting fixtures, a PWM setting of the first color channel such that each of the one or more lighting fixtures irradiate the plant bed at the desired irradiance based on calibration data stored in each of the one or more lighting fixtures, and applying, to each of the one or more lighting fixtures, the determined PWM setting of the first color channel.

FIELD OF THE DISCLOSURE

This disclosure relates to lighting for horticultural applications, andmore particularly to systems and methods for controlling the irradianceof light emitting diode (LED) lighting fixtures.

BACKGROUND

Horticultural systems utilize light sources that emit light of variouswavelengths to encourage plant growth. Generally, in the context ofhorticultural applications light is measured in terms of irradiance,which is the flux of radiant energy per unit area. A common unit formeasuring irradiance is micromoles per square meter per second(μmol/m²-s). Light sources used in horticultural applications are set toemit light with a certain irradiance depending on a number of factors,including the type of plant that is being grown and the distance betweenthe light sources and the plant bed.

SUMMARY

Various implementations disclosed herein may include a method foroperating lighting fixtures in horticultural applications. The methodmay include receiving a user input of a desired irradiance for a firstcolor channel of one or more lighting fixtures that irradiates a plantbed, in which each of the one or more lighting fixtures includes atleast one light emitting diode (LED) array, determining, for each of theone or more lighting fixtures, a pulse width modulation (PWM) setting ofthe first color channel such that each of the one or more lightingfixtures irradiate the plant bed at the desired irradiance based oncalibration data stored in each of the one or more lighting fixtures,and applying, to each of the one or more lighting fixtures, thedetermined PWM setting of the first color channel.

In some embodiments, the one or more lighting fixtures supports aplurality of color channels including the first color channel. In someembodiments, the user input of the desired irradiance is in units ofmicromoles per square meter per second. In some embodiments, thecalibration data includes a total light output of each of the at leastone LED array measured in an integrating sphere, and an irradiance mapof irradiance values of a plurality of color channels, including thefirst color channel, driven at a predetermined PWM setting at apredetermined distance from the lighting fixture. In some embodiments,each lighting fixture is driven at a fixed current and the determinedPWM setting for each of the one or more lighting fixtures is different.In some embodiments, determining, for each of the one or more lightingfixtures, the PWM setting of the first color channel is further based onat least one of a distance between the one or more lighting fixtures andthe plant bed, a layout of the LED array on each of the one or morelighting fixtures, a geometry of the plant bed, a structure of the oneor more lighting fixtures, and optical properties of one or more lenseson each of the one or more lighting fixtures. In some embodiments, thedetermined PWM setting is expressed as a percentage of a maximum currentfor each of the one or more lighting fixtures. In some embodiments, eachlighting fixture stores a plurality of sets of calibration data. In someembodiments, each lighting fixture selects a set of calibration datafrom the plurality of sets of calibration data based on informationreceived from sensors coupled to each lighting fixture.

Additional implementations disclosed herein include a horticulturallighting system, which includes one or more lighting fixtures thatirradiate a plant bed, in which each of the one or more lightingfixtures includes at least one light emitting diode (LED) array and inwhich each of the one or more lighting fixtures stores calibration data,and a controller coupled to the one or more lighting fixtures andconfigured to receive a user input of a desired irradiance for a firstcolor channel of the one or more lighting fixtures, determine, for eachof the one or more lighting fixtures, a pulse width modulation (PWM)setting of the first color channel such that the one or more lightingfixtures irradiates the plant bed at the desired irradiance based on thecalibration data of each of the one or more lighting fixtures, andapply, to each of the one or more lighting fixtures, the determined PWMsetting of the first color channel.

In some embodiments, the one or more lighting fixtures supports aplurality of color channels including the first color channel. In someembodiments, the system further includes a computing devicecommunicatively coupled to the controller, in which the user input istransmitted from the computing device. In some embodiments, the userinput of the desired irradiance is in units of micromoles per squaremeter per second. In some embodiments, the calibration data includes atotal light output of each of the at least one LED array measured in anintegrating sphere, and an irradiance map of irradiance values of aplurality of color channels, including the first color channel, drivenat a predetermined PWM setting at a predetermined distance from thelighting fixture. In some embodiments, each lighting fixture is drivenat a fixed current and the determined PWM setting for each of the one ormore lighting fixtures is different. In some embodiments, each lightingfixture stores a plurality of sets of calibration data, the systemfurther includes one or more sensors coupled to each lighting fixture,and the controller is further configured to select a set of calibrationdata from the plurality of sets of calibration data for each lightingfixture based on information received from the one or more sensorscoupled to each lighting fixture.

Additional implementations disclosed herein include a non-transitoryprocessor-readable storage medium having stored thereon processorexecutable instructions configured to cause a processor of a controllerto perform operations including receiving a user input of a desiredirradiance for a first color channel of one or more lighting fixturesthat irradiates a plant bed, in which each of the one or more lightingfixtures includes at least one light emitting diode (LED) array,determining, for each of the one or more lighting fixtures, a pulsewidth modulation (PWM) setting of the first color channel such that eachof the one or more lighting fixtures irradiate the plant bed at thedesired irradiance based on calibration data stored in each of the oneor more lighting fixtures, and applying, to each of the one or morelighting fixtures, the determined PWM setting of the first colorchannel.

In some embodiments, the calibration data includes a total light outputof each of the at least one LED array measured in an integrating sphere,and an irradiance map of irradiance values of a plurality of colorchannels, including the first color channel, driven at a predeterminedPWM setting at a predetermined distance from the lighting fixture. Insome embodiments, each lighting fixture is driven at a fixed current andthe determined PWM setting for each of the one or more lighting fixturesis different. In some embodiments, the one or more lighting fixturessupports a plurality of color channels including the first colorchannel.

The features and advantages described herein are not all-inclusive and,in particular, many additional features and advantages will be apparentto one of ordinary skill in the art in view of the drawings,specification, and claims. Moreover, it should be noted that thelanguage used in the specification has been selected principally forreadability and instructional purposes and not to limit the scope of theinventive subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a horticultural lighting systemin accordance with various embodiments.

FIG. 2 is a block diagram of a lighting fixture for use in horticulturallighting applications in accordance with various embodiments.

FIG. 3 is a block diagram of a lighting fixture irradiating a plant bedin accordance with various embodiments.

FIG. 4 is an irradiance plot for a lighting fixture including two LEDarrays in accordance with various embodiments.

FIG. 5 is an irradiance plot for three lighting fixtures, each includingtwo LED arrays, in accordance with various embodiments.

FIG. 6 is a user interface for inputting irradiance values to control ahorticultural lighting system in accordance with various embodiments.

FIG. 7 is a flow chart of an example method for operating lightingfixtures in horticultural applications in accordance with variousembodiments.

FIG. 8 is a block diagram illustrating a computing device configured inaccordance with various embodiments.

These and other features of the present embodiments will be understoodbetter by reading the following detailed description, taken togetherwith the figures herein described. The accompanying drawings are notintended to be drawn to scale. For purposes of clarity, not everycomponent may be labeled in every drawing.

DETAILED DESCRIPTION

In many applications, the light output of a light source is usuallymeasured in terms of lumens, optical watts, or micromoles per second.However, in the horticultural field the light output of a light sourcethat irradiates a plant bed is usually measured in terms of irradiance,which may be expressed in micromoles per square meter per second(μmol/m²-s). Prior to using a light source for plant growth, the lightsource is usually characterized and documented. The characterization mayinclude creating an irradiance map of the light source as a function ofheight and lateral position using a calibrated photodiode sensor. Insome cases, a goniometer may also be used to determine the relationshipbetween the light source output and the angular distribution from thelight source. With this characterization, a user (e.g., a person at theplant growth facility) is able to determine the exact irradiance that aplant bed receives when placed under the light source. Thecharacterization of a light source is usually performed manually andtakes a long time. In addition, when one or more elements of the lightsource are replaced (e.g., a lens) or if a different light source isused, then the characterization is performed again as each light sourcemay have slightly different irradiance characteristics. Thus it is timeconsuming to characterize each light source before it can be used in ahorticultural setting.

Thus, and in accordance with various embodiments of the presentdisclosure, systems and methods are disclosed for operating lightingfixtures in horticultural applications. The lighting fixture may be amulti-channel light fixture, meaning it may emit light of multiplecolors. The lighting fixture may include one or more LED arrays.Calibration data may be collected for each color channel of the lightingfixture before being used in a horticultural setting. The calibrationmay be conducted by the manufacturer of the lighting fixture before itis installed in a horticultural lighting system. The calibration datamay include a total light output of each LED array measured in anintegrating sphere, and an irradiance map of irradiance values of eachcolor channel driven at a predetermined PWM setting at a predetermineddistance from the lighting fixture. The calibration data may be storedon the lighting fixture and accessible to devices that control theoperation of the lighting fixture.

The horticultural lighting system may include one or more lightingfixtures lighting a plant bed, each storing its calibration data, one ormore power supplies to power the lighting fixtures, a controller for thelighting fixtures, and a computing device communicatively coupled to thecontroller and/or the lighting fixtures. The computing device mayprovide a user interface for controlling the output of the lightingfixtures. The computing device may receive a user input of a desiredirradiance for a first color channel of one or more lighting fixtures.The computing device, controller, or a processor on the lighting fixturemay determine, for each of the one or more lighting fixtures, a PWMsetting of the first color channel such that each of the one or morelighting fixtures irradiate the plant bed at the desired irradiance. Insome embodiments, each lighting fixture may be driven at a constantcurrent and the PWM setting controls the amount of current that isapplied to the LEDs. In alternative embodiments, the actual currentbeing fed to each lighting fixture may be adjusted to arrive at thedesired irradiance. The determination may be based on the input desiredirradiance, the calibration data, and other factors such as a distancebetween the one or more lighting fixtures and the plant bed, a layout ofthe LED array on each of the one or more lighting fixtures, a geometryof the plant bed, a structure of the one or more lighting fixtures, andoptical properties of one or more lenses on each of the one or morelighting fixtures.

The determined PWM setting for the first color channel is then appliedto each of the one or more lighting fixtures. The desired irradiance maybe expressed as micromoles per square meter per second whereas thedetermined PWM setting may be expressed as a duty cycle, or percentageof a fixed current that drives each of the one or more lightingfixtures. The value of the fixed current for driving a color channelacross all lighting fixtures may depend on the light outputcharacteristics of each lighting fixture. For example, the irradiance ofeach color channel for each lighting fixture may be measured at maximumdrive current. The current associated with the minimum irradiance acrossall lighting fixtures may be chosen as the fixed drive current for alllighting fixtures. Thus, each lighting fixture may be driven to emit thesame irradiance even though their light output characteristics may beslightly different.

By calibrating the lighting fixture before being installed, there is noneed for a person to manually characterize the light source at theinstallation site. Furthermore, a user may input an irradiance value andthe horticultural lighting system may automatically convert the inputinto a PWM setting or current value for each lighting fixture. The userdoes not have to manually convert the desired irradiance into other unitof light output or operating current for the lighting fixture. Overall,the horticultural lighting system disclosed herein may be easier andquicker for a user to set up and operate than prior approaches.

Horticultural Lighting System Architecture

FIG. 1 is a block diagram illustrating a horticultural lighting system100 configured in accordance with various embodiments of the presentdisclosure. The horticultural lighting system 100 may include acomputing device 102. The computing device 102 may be in part or inwhole: (1) a laptop/notebook computer or sub-notebook computer; (2) atablet or phablet computer; (3) a mobile phone or smartphone; (4) apersonal digital assistant (PDA); (5) a portable media player (PMP); (6)a cellular handset; (7) a handheld gaming device; (8) a gaming platform;(9) a desktop computer; (10) a television set; (11) a wearable orotherwise body-borne computing device, such as a smartwatch, smartglasses, or smart headgear; (12) a combination of any one or morethereof, or any other electronic device that includes a processor and amemory.

The computing device 102 may be configured to display a user interfacefor controlling the horticultural lighting system 100, as described infurther detail with reference to FIG. 6. For example, a user may inputinto the user interface a desired irradiance for illuminating one ormore plant beds. The computing device 102 may be communicatively coupledto a controller 106 via a wireless access point 104 or another wirelessor wired access medium. The computing device 102 may transmit the userinput of the desired irradiance to the controller 106.

The controller 106 may be a single board computer or another electroniccomponent that includes at least a processor and a memory. Thecontroller 106 may be configured to convert the desired irradiance to aPWM setting for a fixed current driving one or more lighting fixtures110 such that the lighting fixtures 110 emits the desired irradianceonto the plant beds, and apply the determined PWM setting to the one ormore lighting fixtures 110. In alternative embodiments, the controller106 may adjust the drive current of the one or more lighting fixtures110 to achieve the desired irradiance. In an alternative embodiment, thecomputing device 102 may be configured to convert the desired irradianceto a PWM setting for the one or more lighting fixtures 110 and thecontroller 106 may be configured to apply the determined PWM setting tothe one or more lighting fixtures 110. In another alternativeembodiment, the controller 106 may be configured to transmit the desiredirradiance to the one or more lighting fixtures 110, and each lightingfixture 110 may be configured to convert the desired irradiance to a PWMsetting for that particular lighting fixture. The computing device 102may communicate with the lighting fixtures 110 through an applicationprogramming interfaces (API). The process for converting irradiance to aPWM setting is described in further detail with reference to FIGS. 4-6.

The lighting fixtures 110 may be multi-channel light fixture capable ofemitting multiple colors of light. Each lighting fixture 110 may storecalibration data which may be used to convert the desired irradiance toa PWM setting for that particular lighting fixture. The configurationand layout of the lighting fixtures 110 is described in further detailwith reference to FIG. 2. The lighting fixtures 110 may be connected toone or more power supplies 108, which supply power to the lightingfixtures 110. For example, the power supplies 108 may be 36 Volts directcurrent (DC) power supplies. The horticultural lighting system 100 mayinclude additional components not illustrated in FIG. 1, and the layoutof the horticultural lighting system 100 may be different than asillustrated in FIG. 1. Numerous other such configurations are apparentin light of this disclosure.

Lighting Fixture Layout and Operation

FIG. 2 is a block diagram illustrating the lighting fixture 110configured in accordance with various embodiments of the presentdisclosure. The lighting fixture 110 may include one or more LED arrays202 a, 202 b. Each LED array 202 a, 20 b includes a plurality of LEDs204. Each LED array 202 a, 202 b may be a multi-channel array, meaningthat different LEDs 204 may emit light of different colors. Each LED 204may be tunable and dimmable. For example, LED array 202 a may contain100 LEDs 104 that support seven color channels: 4 LEDs that emitultraviolet light at a wavelength of 380 nanometers (nm), 16 LEDs thatemit blue light at a wavelength of 450 nm, 16 LEDs that emit green lightat a wavelength of 530 nm, 18 LEDs that emit green-shifted white light(“White EQ”) at a center wavelength of 565 nm, 20 LEDs that emit 2700 KCCT white light at a center wavelength of 609 nm, 16 LEDs that emithyper red light at a wavelength of 660 nm, and 10 LEDs that emit far redlight at a wavelength of 730 nm. The LED array 202 b may contain thesame LEDs in the same configuration, or may be configured differentlythan LED array 202 a. The number of LED arrays in a lighting fixture,the number of LEDs for each color channel, the number of color channels,and the wavelength of each color channel are not limited by FIG. 2 andthe present disclosure, but may include numerous other configurations.

The lighting fixture 110 may also include circuitry 206. The circuitry206 may include circuitry for driving and regulating the current drivingthe LEDs 204. The circuitry 206 may also include memory for storingcalibration data particular to the lighting fixture 110. The calibrationdata may include a total light output of each LED array 202 a, 202 bmeasured in an integrating sphere, and an irradiance map of irradiancevalues for each color channel driven at a predetermined PWM setting at apredetermined distance from the lighting fixture 110. The calibrationdata may be generated at the manufacturing facility, before beinginstalled in the horticultural lighting system. In some embodiments, thecircuitry 206 may also include a processor configured to convert areceived desired irradiance (e.g., from a user input on the computingdevice 102) to a PWM setting for the lighting fixture 110. Devicesexternal to the lighting fixture 110 may communicate with the lightingfixture via an API. The lighting fixture 110 may contain additionalcomponents not illustrated in FIG. 2.

The lighting fixture 110 may be installed in a horticultural lightingsystem 300 as illustrated in FIG. 3. One or more lighting fixtures 110may illuminate a plant bed 302. A horticultural lighting system mayinclude a number of plant beds 302, each illuminated by one or morelighting fixtures 110. The irradiance of the lighting fixtures 110 asexperienced by the plant bed 302 is dependent on the height h of thelighting fixtures 110 above plant bed. Generally, the height h ismeasured from the lighting fixtures 110 to the top of the plant canopyof the plant bed 302. The lighting fixtures 110 may be tunable to emitany one or combination of colors onto the plant bed 302, each color at aspecified irradiance value as measured at the plant canopy.

Calibration of Lighting Fixtures and Conversion of Irradiance toPWM/Current

Once each lighting fixture 110 is manufactured but before it is shippedand installed in a horticultural lighting system, the lighting fixture110 may be calibrated and the calibration data may be stored in thelighting fixture 110. The calibration data may be used to determine thePWM setting for the lighting fixture 110 in order to achieve a specifiedirradiance value for a plant bed.

The calibration data may include the total light output (in lumens) ofeach color channel for each board of LED arrays 202 a, 202 b, measuredin an integrating sphere. The integrating sphere measurements may bemade at several different PWM values for the LED array boards, forexample at 20%, 40%, 60%, 80%, and 100% duty cycle for each colorchannel of each LED array board. In some embodiments, each color channelof each LED array board being measured may be driven at the same drivecurrent. The integrating sphere measurements may be used to generatepolynomials for each color channel of each LED array board that relatenormalized radiated power to PWM values. For example, the maximum lightoutput (i.e., at 100% duty cycle) and the coefficients of a curve fittedto the output versus duty cycle for each color channel of a LED arrayboard may be stored in memory on the lighting fixture that contains theLED array board.

The calibration data may also include an irradiance measurement for eachcolor channel of each LED array board, driven at a predetermined PWMsetting and measured at a predetermined distance from the lightingfixture. The predetermined distance may be a planned or a typical heightfrom the lighting fixture to the plant canopy of a plant bed. Theirradiance at a given height depends on the maximum light output of theLED array board and the distribution of the light output. The lightoutput distribution depends on a number of factors, including thepredetermined height, arrangement of LEDs on the LED array board, thearrangement of the boards on the lighting fixtures, and the lenses orother optics on each LED array board. If each LED array board isdesigned the same, the distribution would be the same. The irradiancemeasurement may take the form of an irradiance map or table ofirradiance values in a plane parallel to the lighting fixture at adistance equal to the predetermined distance from the lighting fixture.For example, if the predetermined distance is 16 inches, then anirradiance area of one square meter, at 25 millimeter (mm) LED spacing,may be sufficient to map the performance of an LED array board. Thepredetermined PWM setting may be, for example, 100% duty cycle for eachLED array board. The irradiance measurements may be made using a XYtable, a calibrated irradiance meter, and automated software.

If each LED array board on each lighting fixture are the same (e.g.,same number of LEDs of each color, same wavelength, same layout), thenthe irradiance map for one LED array board may be measured and theresults may be duplicated for the other LED array boards andsuperimposed to produce an irradiance map for multiple LED arrays andlighting fixtures. For example, FIG. 4 shows an irradiance plot 400 fora lighting fixture including two LED array boards in accordance withvarious embodiments, such as the lighting fixture 110 as illustrated inFIG. 2. If both LED array boards in the lighting fixture are the same,then the irradiance may be measured for one LED array board and thenduplicated for the second LED array board. The irradiance plot 400 maybe a superposition of the irradiance measurements for each LED arrayboard, assuming that the LED array boards are driven to emit the sameirradiance at the predetermined distance. For example, the two peaks inthe irradiance plot 400 correspond to the centers of each LED arrayboard, and the irradiance value at a particular point of the irradianceplot 400 is the sum of the irradiance measurements of each LED arrayboard at that point. As can be seen, the irradiant light forms acircular pattern with the highest intensity at the center of the LEDarray board.

The irradiance distribution as seen in the irradiance plot 400 remainsthe same given the same predetermined distance and fixed optics on theLED array board, but the absolute value of the irradiance within thedistribution changes with different drive currents. However, because thedistribution is constant the irradiance measurement can be performed ata single current and scaled with the value of the driving current.

FIG. 5 shows an irradiance plot 500 for three lighting fixturesilluminating a plant bed, each including two LED array boards, inaccordance with various embodiments. Assuming each LED array board ineach lighting fixture is the same, then the irradiance plot 400 may beduplicated for each lighting fixture and the irradiance plot 500 may bea superposition of the irradiance map for each individual lightingfixture. In other words, the irradiance value at a particular point ofthe irradiance plot 500 is the sum of the irradiance measurements ofeach LED array board of each lighting fixture at that point. Theirradiance plot 500 may be truncated to fit the dimensions of a plantbed, as shown in FIG. 5. The average irradiance of the irradiance plot500 may be calculated, and an irradiance map may be generated that isnormalized to the average irradiance.

FIG. 6 shows a user interface 600 for inputting irradiance values to ahorticultural lighting system in accordance with various embodiments.The user interface 600 may be presented at a computing devicecommunicatively connected to the lighting fixtures, such as computingdevice 102 in FIG. 1. The user interface 600 may include an irradiancemap 602. The irradiance map 602 may show an overhead distribution of theirradiance plot 500 normalized to the average irradiance. An absoluteirradiance map may be generated by multiplying the values in theirradiance map 602 by the average irradiance value. In the context ofcontrolling the irradiance of the lighting fixtures, the absoluteirradiance map may be generated by multiplying the values in theirradiance map 602 by the desired irradiance value.

The calibration data may also include information relating theintegrating sphere light output measurements with the irradiancemeasurements. This information may take the form of a “sphere factor.”When the irradiance measurements for a single LED array is integrated,the result equals the amount of total energy per time striking themeasurement area (e.g., one square meter). Dividing the result by theintegrating sphere total light output value equals the sphere factor.Thus the calibration may include calculating the sphere factor for eachcolor channel. The integrating sphere total light output value includesall light emitted from the LED array, but not all of the light emittedby an LED array strikes the plant bed. This light loss is embodied inthe sphere factor, as it is always less than one. For example, if thesphere factor for a color channel is 0.86, then a 1 Watt (W) total lightoutput value in the integrating square would equal 0.86 W of radiatedlight that strikes the area centered below the LED array at a distanceequal to the predetermined distance.

The calibration data is dependent upon a number of factors. Thesefactors may include the height of the lighting fixture above the plantbed, the size of the plant bed, the lenses affixed on the LEDs, thelighting fixture structure and geometry (e.g., shape, dimensions,presence of diffuser cover), and the layout of the LEDs. If any of thesefactors are changed, the lighting fixture should be recalibrated and thenew calibration data is stored in the memory of the lighting fixture.The calibration data may include different sets of data corresponding tochanges in one or more of the factors so that certain changes may bemade without having to recalibrate the lighting fixture. For example,the lighting fixture may store calibration data for different distancesbetween the plant bed and the lighting fixture to account for thevertical growth of plants over time. In some embodiments, the lightingfixture may receive information from sensors coupled to the lightingfixture. The sensors may detect the height of the lighting fixture fromthe plant bed and the spacing between the lighting fixtures. With thisinformation, the lighting fixture may select the appropriate calibrationdata stored in memory.

The user interface 600 illustrated in FIG. 6 also includes an irradianceinput 604, which allows a user to input a desired irradiance for eachcolor channel of one or more lighting fixtures irradiating one or moreplant beds. The input irradiance may be in units of micromoles persquare meter per second (μmol/m²-s). The irradiance input 604 may alsoinclude a slider for each color channel that may be used to change thedesired irradiance between a minimum value and a maximum value. Theirradiance input 604 is not limited to the interface as shown in FIG. 6,but may be presented in numerous configurations known in the art. Whenthe user inputs a desired irradiance for a selected color channel, thecomputing device may communicate the desired irradiance to a controller,which converts the desired irradiance into a PWM setting for theselected color channel of the one or more lighting fixtures and thenapplies the determined PWM setting. The irradiance map 602 may beupdated in real time based on the user input.

There are a number of ways to determine a PWM setting for a colorchannel of one or more lighting fixtures from a desired irradiance. Onemethod is described below, but the present disclosure is not limited tothe described method but may encompass numerous methods known in theart. First, the desired irradiance may be multiplied by the area of theplant bed irradiated by the lighting fixtures, and the result is dividedby a plant bed canopy factor. The plant bed canopy factor represents thefraction of light generated by the lighting fixture that actuallystrikes the plant bed, and is a function of the height of the lightingfixture above the plant bed, the spacing of the LED arrays on eachlighting fixture, the spacing between lighting fixtures, the opticalelements on each lighting fixture, and the color of the selected colorchannel. The result is then divided by the number of LED arrays in thelighting fixtures to yield a value representing the number of micromolesper second emitted by a single LED array.

This value is divided by a color factor, which is specific to thewavelength of the color of the color channel (e.g., 3.76 μMol/W-sec forblue light at 450 nm), to yield the watts irradiated per LED array. Thisvalue is divided by the sphere factor (stored in the calibration data)to obtain the desired spherical watts equivalent to the desiredirradiance. This value is divided by the integrating sphere total lightoutput at maximum current (stored in the calibration data) to obtain anormalized watt output (i.e., between zero and one). Polynomials thatrelate normalized radiated power to percentage of full DC current(stored in the calibration data) are applied to the normalized wattoutput to obtain the percentage of maximum current for the color channelthat is equivalent to the desired irradiance. The color channel of thelighting fixtures may then be driven with a fixed current with aspecific pulse width modulated (PWM) value or duty cycle so that theactual current matches the calculated percentage of the maximum current.In some embodiments, the process for converting desired irradiance to aPWM setting may also include correcting for temperature and run time ofthe lighting fixture.

Each lighting fixture has different lighting characteristics and thusdifferent calibration data due to small differences that occur duringmanufacturing of the LEDs, even if all lighting fixtures are designed tobe the same. The horticultural lighting system described hereincompensates for these differences through the calibration data. Forexample, the light output (in lumens) of each color channel for eachlighting fixture may be measured when each lighting fixture is driven atits maximum duty cycle and the value is stored in memory on eachlighting fixture. The controller may query each lighting fixture for themaximum light output for each color channel and store the maximum valuesin memory. The controller may reuse these values as long as none of thelighting fixtures are changed or replaced. The controller takes thesmallest of the maximum light output for each color channel and setsthat value as the maximum allowable light output for each lightingfixture. Although each lighting fixture is driven by the same current,different PWM settings may be applied to each lighting fixture. A usermay input a single desired irradiance for a color channel across severallighting fixtures, and the system determines the PWM setting for eachlighting fixture (which may be different) such that all the lightingfixtures emit equal irradiances for that color channel. This avoids theneed for a user to manually tune each lighting fixture to achieve equalirradiances. For example, a user may input a desired irradiance for acolor channel equal to the maximum allowable light output across alllighting fixtures. The controller would drive the color channel of thelighting fixture with the smallest maximum light output at 100% dutycycle, but would scale the duty cycles of the other lighting fixtures(e.g., 75%, 50%) to match the irradiance of the lighting fixture withthe smallest maximum light output. This method ensures uniformirradiance across all lighting fixtures even though each individuallighting fixture has different light output characteristics.

Example Methods for Operating a Horticultural Lighting System

FIG. 7 is a flow chart of an example method 700 for operating ahorticultural lighting system in accordance with various embodiments ofthe present disclosure. The method 700 may be performed by one or acombination of a computing device (e.g., computing device 102), acontroller (e.g., controller 106), and one or more lighting fixtures(e.g., lighting fixture 110) in a horticultural lighting system such asillustrated in FIG. 1. The computing device may be communicativelycoupled to the controller via a wired or wireless connection (e.g., aWiFi router). The controller may control the PWM settings of the one ormore lighting fixtures. Each lighting fixture may support a plurality ofcolor channels, and may each include one or more LED arrays such as LEDarrays 202 a, 202 b illustrated in FIG. 2.

In block 702, the computing device may receive a user input of a desiredirradiance for a first color channel of one or more lighting fixturesthat irradiate a plant bed. The computing device may display a userinterface (e.g., user interface 600 shown in FIG. 6) that allows a userto input a desired irradiance. In some embodiments, the units of theinput irradiance may be micromoles per square meter per second(μmol/m²-s). The controller may receive the user input from thecomputing device.

In block 704, the controller may determine, for each of the one or morelighting fixtures, a PWM setting of the first color channel such thateach of the lighting fixtures irradiate the plant bed at the desiredirradiance based on calibration data stored in each lighting fixture. Anexample method for converting a desired irradiance to a PWM setting forcolor channel of a lighting fixture is described in further detail withreference to FIG. 6. In summary, the desired irradiance may bemultiplied by the area of the plant bed, divided by a plant bed canopyfactor, then divided by the number of LED arrays in the lightingfixtures, then divided by a color factor, then divided by the spherefactor, then divided by the integrating sphere total light output atmaximum current. Polynomials that relate normalized radiated power topercentage of full DC current are applied to the result to obtain thepercentage of maximum current for the color channel that is equivalentto the desired irradiance. In some embodiments, the method forconverting desired irradiance to a PWM setting may also includecorrecting for temperature and run time of the lighting fixture.

In alternative embodiments, the computing device may determine the PWMsetting and transmit the PWM setting to the controller. In otheralternative embodiments, each lighting fixture may receive the desiredirradiance from the controller and determine its own PWM setting. Thecomputing device may communicate with the controller and the lightingfixtures through an API.

The calibration data may be stored in memory on each lighting fixtureand are specific to each lighting fixture. The calibration data mayinclude a total light output of each of the LED arrays in the lightingfixture measured in an integrating sphere, and an irradiance map/tableof irradiance values of each color channel driven at a predetermined PWMsetting at a predetermined distance from the lighting fixture. In someembodiments, the calibration data may also include information relatingthe integrating sphere light output measurements with the irradiancemeasurements, such as a sphere factor that is equal to the integral ofthe irradiance measurement for a single LED array divided by theintegrating sphere total light output. In some embodiments, thecalibration data may also include polynomials that relate normalizedradiated power to percentage of full DC current. Methods for generatingthe calibration data are described in further detail with reference toFIGS. 4-5. The calibration data may be generated after manufacturing andbefore it is installed in the horticultural lighting system.

The calibration data may depend on a number of factors, including theheight of the lighting fixture above the plant bed, the size of theplant bed, the lenses affixed on the LEDs, the lighting fixturestructure and geometry (e.g., shape, dimensions, presence of diffusercover), and the layout of the LEDs. In some embodiments, if one or moreof the factors change the lighting fixture is recalibrated in order togenerate updated calibration data. In some embodiments, the calibrationdata may include different sets of data corresponding to changes in oneor more of the factors. For example, the lighting fixture may storecalibration data for different distances between the plant bed and thelighting fixture to account for the vertical growth of plants over time.In some embodiments, the lighting fixture may receive information fromsensors coupled to the lighting fixture. The sensors may detect theheight of the lighting fixture from the plant bed and the spacingbetween the lighting fixtures. With this information, the lightingfixture may select the appropriate calibration data stored in memory.

In block 706, the controller may apply, to each of the one or morelighting fixtures, the determined PWM setting of the first colorchannel. For example, the controller may change the pulse widthmodulation (PWM) value applied to a fixed current driving the colorchannel on each lighting fixture. Each lighting fixture may be driven bythe same fixed current but may have a different PWM setting to achievethe same desired irradiance because of material or manufacturingdifferences in each lighting fixture. The controller may apply differentPWM settings to each lighting fixture so that all of the lightingfixtures emit the same irradiance. In alternative embodiments, thecontroller may adjust the actual current driving each of the one or morelighting fixtures to achieve the desired radiance. The user interface onthe computing device may include an irradiance map that changes in realtime based on the user input. The method may then return to block 702when the user inputs another desired irradiance for the same or adifferent color channel. In this manner, the method 700 allows a user toinput a desired irradiance for a color channel in order to change thePWM setting of one or more lighting fixtures to achieve uniformirradiance across all the lighting fixtures.

Further Considerations

FIG. 8 illustrates an example computing device 800 configured inaccordance with various embodiments of the present disclosure. Thecomputing device 800 may be similar to the computing device 102 and thecontroller 106 in FIG. 1, and the circuitry 206 in FIG. 2. The computingdevice 800 can be any of a wide range of computing platforms, mobile orotherwise. For example, in accordance with some embodiments, computingdevice 800 can be, in part or in whole: (1) a laptop/notebook computeror sub-notebook computer; (2) a tablet or phablet computer; (3) a mobilephone or smartphone; (4) a personal digital assistant (PDA); (5) aportable media player (PMP); (6) a cellular handset; (7) a handheldgaming device; (8) a gaming platform; (9) a desktop computer; (10) atelevision set; (11) a wearable or otherwise body-borne computingdevice, such as a smartwatch, smart glasses, or smart headgear; (12) asingle board computer or microprocessor circuit; and/or (13) acombination of any one or more thereof. Other suitable configurationsfor computing device 800 will depend on a given application and will beapparent in light of this disclosure.

As can be further seen from FIG. 8, computing device 800 may includememory 804 and one or more processors 802. Memory 804 can be of anysuitable type (e.g., RAM and/or ROM, or other suitable memory) and size,and in some cases may be implemented with volatile memory, non-volatilememory, or a combination thereof. A given processor 802 of the computingdevice 800 may be configured as typically done, and in some embodimentsmay be configured, for example, to perform operations associated withcomputing device 800 and one or more of the components thereof (e.g.,within memory 804 or elsewhere). In some cases, memory 804 may beconfigured to be utilized, for example, for processor workspace (e.g.,for one or more processors 802) and/or to store media, programs,applications, and/or content on computing device 800 on a temporary orpermanent basis. The one or more components may be stored in memory 804(e.g., such as an operating system (OS), user interface, and/or one ormore applications) and can be accessed and executed, for example, by theone or more processors 802 of computing device 800. In some embodiments,the memory 802 of the computing device 800 may calibration data for alighting fixture.

The OS can be implemented with any suitable OS, mobile or otherwise,such as, for example: (1) Android OS from Google, Inc.; (2) iOS fromApple, Inc.; (3) BlackBerry OS from BlackBerry Ltd.; (4) Windows PhoneOS from Microsoft Corp; (5) Palm OS/Garnet OS from Palm, Inc.; (6) anopen source OS, such as Symbian OS; and/or (7) a combination of any oneor more thereof. Suitable configurations and capabilities for the OSwill depend on a given application and will be apparent in light of thisdisclosure. A user interface (UI) is provided as commonly done, andgenerally allows for user interaction with the device 800 (e.g., such asa graphical touched-based UI on various smartphones and tablets). Anynumber of user interface schemes can be used.

In accordance with some embodiments, memory 804 may have stored therein(or otherwise have access to) one or more applications. In someinstances, computing device 800 may be configured to receive input, forexample, via one or more applications stored in memory 804 (e.g., suchas an application for controlling a horticultural lighting system). Inaccordance with some embodiments, a given application can be implementedin any suitable standard and/or custom/proprietary programming language,such as, for example: (1) C; (2) C++; (3) objective C; (4) JavaScript;and/or (5) any other suitable custom or proprietary instruction sets. Ina more general sense, the applications can be instructions encoded onany suitable non-transitory machine-readable medium that, when executedby one or more processors 802, carries out functionality of a givencomputing device 800, in part or in whole. In one example embodiment,one of the applications may be an application for controlling ahorticultural lighting system in which a user may input a desiredirradiance of a color channel for one or more lighting fixtures in thehorticultural lighting system.

As can be seen further from FIG. 8, computing device 800 may include adisplay 806, in accordance with some embodiments. Display 806 can be anyelectronic visual display or other device configured to display orotherwise generate an image (e.g., image, video, text, and/or otherdisplayable content) there at. In some instances, display 806 may beintegrated, in part or in whole, with computing device 800, whereas insome other instances, display 806 may be a stand-alone componentconfigured to communicate with computing device 800 using any suitablewired and/or wireless communications means. In some cases, display 806optionally may be a touchscreen display or other touch-sensitivedisplay. To that end, display 806 may utilize any of a wide range oftouch-sensing techniques, such as, for example: (1) resistivetouch-sensing; (2) capacitive touch-sensing; (3) surface acoustic wave(SAW) touch-sensing; (4) infrared (IR) touch-sensing; (5) opticalimaging touch-sensing; and/or (6) a combination of any one or morethereof. In a more general sense, and in accordance with someembodiments, an optionally touch-sensitive display 806 generally may beconfigured to detect or otherwise sense direct and/or proximate contactfrom a user's finger, stylus, or other suitable implement at a givenlocation of that display 806. In some cases, an optionallytouch-sensitive display 806 may be configured to translate such contactinto an electronic signal that can be processed by computing device 800(e.g., by the one or more processors 802 thereof) and manipulated orotherwise used to trigger a given UI action. In some cases, atouch-sensitive display 806 may facilitate user interaction withcomputing device 800 via the UI presented by such display 806. Numeroussuitable configurations for display 806 will be apparent in light ofthis disclosure.

In accordance with some embodiments, computing device 800 may include acommunication unit 808, which may be configured for wired (e.g.,Universal Serial Bus or USB, Ethernet, FireWire, etc.) and/or wireless(e.g., Wi-Fi, Bluetooth, etc.) communication using any suitable wiredand/or wireless transmission technologies (e.g., radio frequency, or RF,transmission; infrared, or IR, light modulation; etc.), as desired. Inaccordance with some embodiments, communication unit 808 may beconfigured to communicate locally and/or remotely utilizing any of awide range of wired and/or wireless communications protocols, including,for example: (1) a digital multiplexer (DMX) interface protocol; (2) aWi-Fi protocol; (3) a Bluetooth protocol; (4) a digital addressablelighting interface (DALI) protocol; (5) a ZigBee protocol; (6) a nearfield communication (NFC) protocol; (7) a local area network (LAN)-basedcommunication protocol; (8) a cellular-based communication protocol; (9)an Internet-based communication protocol; (10) a satellite-basedcommunication protocol; and/or (11) a combination of any one or morethereof. It should be noted, however, that the present disclosure is notso limited to only these example communications protocols, as in a moregeneral sense, and in accordance with some embodiments, any suitablecommunications protocol, wired and/or wireless, standard and/orcustom/proprietary, may be utilized by communication unit 808, asdesired for a given target application or end-use. Numerous suitableconfigurations for communication unit 808 will depend on a givenapplication and will be apparent in light of this disclosure.

As can be seen further from FIG. 8, computing device 800 may include oneor more input/output devices 810. Examples of input/output devices 810may include a keyboard, mouse, speakers, microphone, touchscreen(integrated with the display 806), USB and other ports, and/or otherforms of input and output known in the art. A user may utilize one ormore input devices to input information to the computing device 800, andthe computing device may utilize one or more output devices tocommunication information to the user. The processor(s) 802, memory 804,display 806, communication unit 808, and input/output devices 810 may beconnected together through bus 812. The computing device 800 may includeadditional components not shown in FIG. 8, such as but not limited toadditional processors (e.g., graphic processors), sensors,microcontrollers, and image capture devices (e.g., cameras).

The foregoing description of the embodiments of the present disclosurehas been presented for the purposes of illustration and description. Itis not intended to be exhaustive or to limit the present disclosure tothe precise form disclosed. Many modifications and variations arepossible in light of this disclosure. It is intended that the scope ofthe present disclosure be limited not by this detailed description, butrather by the claims appended hereto.

1. A method for operating lighting fixtures in horticulturalapplications, the method comprising: receiving a user input of a desiredirradiance for a first color channel of one or more lighting fixturesthat irradiates a plant bed, wherein each of the one or more lightingfixtures comprises at least one light emitting diode (LED) array;determining, for each of the one or more lighting fixtures, a pulsewidth modulation (PWM) setting of the first color channel such that eachof the one or more lighting fixtures irradiate the plant bed at thedesired irradiance based on calibration data stored in each of the oneor more lighting fixtures; and applying, to each of the one or morelighting fixtures, the determined PWM setting of the first colorchannel.
 2. The method of claim 1, wherein the one or more lightingfixtures supports a plurality of color channels including the firstcolor channel.
 3. The method of claim 1, wherein the user input of thedesired irradiance is in units of micromoles per square meter persecond.
 4. The method of claim 1, wherein the calibration datacomprises: a total light output of each of the at least one LED arraymeasured in an integrating sphere; and an irradiance map of irradiancevalues of a plurality of color channels, including the first colorchannel, driven at a predetermined PWM setting at a predetermineddistance from the lighting fixture.
 5. The method of claim 1, whereineach lighting fixture is driven at a fixed current and the determinedPWM setting for each of the one or more lighting fixtures is different.6. The method of claim 1, wherein determining, for each of the one ormore lighting fixtures, the PWM setting of the first color channel isfurther based on at least one of a distance between the one or morelighting fixtures and the plant bed, a layout of the LED array on eachof the one or more lighting fixtures, a geometry of the plant bed, astructure of the one or more lighting fixtures, and optical propertiesof one or more lenses on each of the one or more lighting fixtures. 7.The method of claim 1, wherein the determined PWM setting is expressedas a percentage of a maximum current for each of the one or morelighting fixtures.
 8. The method of claim 1, wherein each lightingfixture stores a plurality of sets of calibration data.
 9. The method ofclaim 8, wherein each lighting fixture selects a set of calibration datafrom the plurality of sets of calibration data based on informationreceived from sensors coupled to each lighting fixture.
 10. Ahorticultural lighting system, comprising: one or more lighting fixturesthat irradiate a plant bed, wherein each of the one or more lightingfixtures comprises at least one light emitting diode (LED) array andwherein each of the one or more lighting fixtures stores calibrationdata; and a controller coupled to the one or more lighting fixtures andconfigured to: receive a user input of a desired irradiance for a firstcolor channel of the one or more lighting fixtures; determine, for eachof the one or more lighting fixtures, a pulse width modulation (PWM)setting of the first color channel such that the one or more lightingfixtures irradiates the plant bed at the desired irradiance based on thecalibration data of each of the one or more lighting fixtures; andapply, to each of the one or more lighting fixtures, the determined PWMsetting of the first color channel.
 11. The system of claim 10, whereinthe one or more lighting fixtures supports a plurality of color channelsincluding the first color channel.
 12. The system of claim 10, furthercomprising a computing device communicatively coupled to the controller,wherein the user input is transmitted from the computing device.
 13. Thesystem of claim 10, wherein the user input of the desired irradiance isin units of micromoles per square meter per second.
 14. The system ofclaim 10, wherein the calibration data comprises: a total light outputof each of the at least one LED array measured in an integrating sphere;and an irradiance map of irradiance values of a plurality of colorchannels, including the first color channel, driven at a predeterminedPWM setting at a predetermined distance from the lighting fixture. 15.The system of claim 10, wherein each lighting fixture is driven at afixed current and the determined PWM setting for each of the one or morelighting fixtures is different.
 16. The system of claim 10, wherein:each lighting fixture stores a plurality of sets of calibration data;the system further comprises one or more sensors coupled to eachlighting fixture; and the controller is further configured to select aset of calibration data from the plurality of sets of calibration datafor each lighting fixture based on information received from the one ormore sensors coupled to each lighting fixture.
 17. A non-transitoryprocessor-readable storage medium having stored thereon processorexecutable instructions configured to cause a processor of a controllerto perform operations comprising: receiving a user input of a desiredirradiance for a first color channel of one or more lighting fixturesthat irradiates a plant bed, wherein each of the one or more lightingfixtures comprises at least one light emitting diode (LED) array;determining, for each of the one or more lighting fixtures, a pulsewidth modulation (PWM) setting of the first color channel such that eachof the one or more lighting fixtures irradiate the plant bed at thedesired irradiance based on calibration data stored in each of the oneor more lighting fixtures; and applying, to each of the one or morelighting fixtures, the determined PWM setting of the first colorchannel.
 18. The non-transitory processor-readable storage medium ofclaim 17, wherein the calibration data comprises: a total light outputof each of the at least one LED array measured in an integrating sphere;and an irradiance map of irradiance values of a plurality of colorchannels, including the first color channel, driven at a predeterminedPWM setting at a predetermined distance from the lighting fixture. 19.The non-transitory processor-readable storage medium of claim 17,wherein each lighting fixture is driven at a fixed current and thedetermined PWM setting for each of the one or more lighting fixtures isdifferent.
 20. The non-transitory processor-readable storage medium ofclaim 17, wherein the one or more lighting fixtures supports a pluralityof color channels including the first color channel.